Cosmetic problem with new menu in Firefox

Hi,

I've been testing RC (CVS) for a few days now and am impressed with the clean look and the speed. I've noticed one problem that no one else seems to be reporting on. Since the move of the menu items from the bottom of the webpage to the upper portion, I have been seeing that part of the menu bar distorted (blackened). It appeared normally when it was located at the bottom, and it currently appears normally in IE. I am thinking it might just be a FF problem. Anyway, just thought I would make you aware and ask if you had any suggestions for resolving it. I'm running the latest nightly build of FF on a Dell Inspiron @1600x1200.

I'm attaching a small jpg to illustrate what I am seeing. Thanks, Glen